The monitoring of water colour parameters can provide an important diagnostic tool for the assessment of aquatic ecosystem condition. Remote sensing has long been used to effectively monitor chlorophyll concentrations in open ocean systems; however, operational monitoring in coastal and estuarine areas has been limited because of the inherent complexities of coastal systems, and the coarse spectral and spatial resolutions of available satellite systems. Data were collected using the National Aeronautics and Space Administration (NASA) Advanced Visible-Infrared Imaging Spectrometer (AVIRIS) flown at an altitude of approximately 20 000 m to provide hyperspectral imagery and simulate both MEdium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectrometer (MODIS) data. AVIRIS data were atmospherically corrected using a radiative transfer modelling approach and analysed using band ratio and linear regression models. Regression analysis was performed with simultaneous field measurements data in the Neuse River Estuary (NRE) and Pamlico Sound on 15 May 2002. Chlorophyll a (Chl a) concentrations were optimally estimated using AVIRIS bands (9.5 nm) centred at 673.6 and 692.7 nm, resulting in a coefficient of determination (R 2) of 0.98. Concentrations of Chromophoric Dissolved Organic Matter (CDOM), Total Suspended Solids (TSS) and Fixed Suspended Solids (FSS) were also estimated, resulting in coefficients of determination of R 2 = 0.90, 0.59 and 0.64, respectively. Ratios of AVIRIS bands centred at or near those corresponding to the MERIS and MODIS sensors indicated that relatively good satellite-based estimates could potentially be derived for water colour constituents at a spatial resolution of 300 and 500 m, respectively.

In response to recent water quality declines, caused by excessive nitrogen (N) loading, a 30% reduction of N inputs into the Neuse River Estuary (NRE) has been mandated by the North Carolina State Legislature. Water quality model predictions as well as nutrient bioassays indicate that a 30% reduction in N will result in a 15% reduction in phytoplankton biomass (as chlorophyll a) in the NRE. Using previously published NRE light extinction coefficient component data and NRE irradiance data, we calculated that the average NRE compensation depth (<1% surface irradiance) would deepen by 13cm following a 15% reduction in phytoplankton biomass. Hydrographic and bathymetry data were used in a Geographical Information System to plot the resulting increase in euphotic sediment surface area based on the predicted change in the compensation depth. The newly created euphotic sediment surface area represents 4.47 X 10(6) m(2) which is 20% larger than the average sediment surface area in the euphotic zone during the study period (1998-2000).Previous NRE work revealed that euphotic sediment in the NRE support autotrophic benthic microalgal communities (BMC) that alter oxygen and nutrient fluxes. To further quantify this effect, we conducted a series of light versus dark incubations of NRE sediments collected from above (shallow euphotic areas < 1 in water depth) and below (deep aphotic areas > 3.5 m water depth) the compensation depth. Sediment oxygen demand (SOD), nutrient flux and organic matter content were significantly lower in shallow water cores compared to their deep-water counterparts. Furthermore, the illuminated shallow cores demonstrated a 45% decrease in SOD compared to shallow cores incubated in the dark. The combined effect of the projected increase in BMC habitat coupled with the reduction in SOD and nutrient flux associated with BMC represents an overlooked and potentially important benefit of reduced N inputs that could accelerate water quality recovery in the NRE. (C) 2004 Elsevier Ltd. All rights reserved.